1. Field of the Invention
This invention relates to apparatus for electrically initiating release of a ski binding in response to a signal which is proportional to the tensile, compressive or torsional force between the ski boot and the ski.
2. State of the Art
In order to achieve the optimum safety and convenience of handling of skis, it is necessary for each boot of the skier to be fixed rigidly with respect to the ski. However, in the event of a potentially dangerous fall, it is extremely important to disengage the ski boots from the skis, in order to minimize the possibility of injury. As a result of these hazards, safety bindings have been developed for the purpose of releasably fastening a ski boot to a ski, so that the ski boot is rigidly fixed to the ski during normal conditions of use, and whereby extreme bending, tensile or compressive forces on the ski that may occur during a fall would operate to actuate a release mechanism to unclamp the ski boot with respect to the ski, so that the ski, during fall, could separate from the boot, thereby lessening the risk of injury to the skier.
Many types of safety bindings exist, and some of the commonly utilized bindings are the Cubco, Tyrolia, Marker, Spademan, Americana, Gertsch, Look Nevada, Rosemount and Salomon bindings.
One of the most recent binding developments is the Spademan binding, which, unlike most of the other bindings, engages the ski boot at the sides, rather than at the heel and toe. The general design of a Spademan binding is illustrated in U.S. Pat. No. Re. 26,972.
The current state-of-the-art ski bindings are operative for their intended purpose, to some extent. However, they have numerous shortcomings. Among these are the fact that all release systems presently available require significant rotational movement between the ski and boot, in order to actuate the release mechanism. This movement is, of course, accompanied by a frictional force which resists this movement. If the friction were constant, it could be assumed that a reliable mechanical system of a highly predictable nature would function safely and accurately. However, this is not the case, because the frictional forces that must be overcome are a function of the particular orientation of the skier and the amount of dirt or ice between or around the moving surfaces during the fall. Accordingly, all of the current state-of-the-art ski bindings, although they are initially adjustable by setting the spring force which must be overcome in order to obtain release of the binding, do not, in practice, function in the intended manner and are therefore not completely reliable and predictable. This is so because of the snow and dirt which accumulates between the ski boot and the ski binding or surface and because of the varying angles at which force is applied between the ski boot and ski binding and surface. Too, when a free fall occurs, the downward force between the ski and boot may be much greater than the force which is assumed when the release is "set" in a test fixture. Therefore, in a real free fall situation significantly larger additional side loads may be required to get sufficient movement of the boot relative to the ski to effect release.
Moreover, the current state-of-the-art bindings do not make provision for the effect of time with respect to any given force, in determining when the ski should be released. For example, an aggressive skier, when skiing, will impose very high forces on his skis in the normal and usual course of skiing. These substantial forces will usually be of relatively short duration and high magnitude, and must be accommodated, if possible, in the ski binding system. However, if the same magnitude of force were to be applied for a greater duration, substantial injury could occur to the skier. On the other hand, substantially lower forces applied through longer periods of time, could also do substantial damage to the skier. Accordingly, although none of the state-of-the-art devices provides such a feature, it is desirable to have a ski release system which is actuated by certain predetermined forces which are operative on the ski and boot, but which takes into account the element of time, so that the ski boot is released only when the applied force presents a hazard to the skier.